<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        span{
            color: green;
        }
    </style>

    <link href="../css/demo.css" rel="stylesheet">
</head>
<body>
    <div style="color: red">hello css</div>

    <span>hello css</span>

    <p>hello_css</p>
</body>
</html>